Washington: Scientists have identified a type of gut bacteria that can directly influences brain, a finding they say could lead to new ways to control depression and other psychiatric disorders.

Researchers have long suspected that the gut was somehow linked with the brain, since bowel disorders are linked with stress-related psychiatric disorders such as anxiety and depression in people.

To learn more, a team at the University College Cork in Ireland fed laboratory mice with Lactobacillus rhamnosus JB-1, a bug that naturally lives in human gut.

The researchers found that the mice, which were given the bug-laced broth, displayed significantly less behaviour linked with stress, anxiety and depression than mice fed plain broth.

Bacteria-fed mice also had significantly lower levels of the stress hormone corticosterone in response to stressful situations such as mazes, LiveScience reported.

As mice serve as good models for understanding aspects of the human brain, the findings can be replicated in humans too, the researchers said.

"By affecting gut bacteria, you can have very robust and quite broad-spectrum effects on brain chemistry and behaviour," study researcher John Cryan said.

Cryan said: "Without overstating things, this does open up the concept that we could develop therapies that can treat psychiatric disorders by targeting the gut.”

"You could take a yogurt with a probiotic in it instead of an antidepressant," he added.

"Now, that would not be an everyday yogurt -- I'm not saying you should go out to the supermarket and try doing this," he cautioned.

"The effect depends on the strain of probiotic you use. The hope would be, though, that this could have fewer side effects than drugs." Stimulations of vagus nerve -- which helps alert the central nervous system to changes in the gastrointestinal tract -- have been used at times to treat depression resistant to other therapies.

"That's a surgical technique. But by targeting the gut with probiotics, we could indirectly target the vagus nerve without surgery," said Cryan.

Detailing their findings in the journal Proceedings of the National Academy of Sciences, the researchers said follow-up studies will investigate whether these bacteria have this effect alive or dead, to see if it is due to either something the microbes are equipped with or release.

Further studies can also tease out whether the gut can affect other brain chemicals such as serotonin and dopamine, which have been linked with mood, among other factors, they added.